Compositions and Methods for Controlling Weeds in Crops

ABSTRACT

Compositions and methods for controlling volunteer crop weeds in a crop by applying to weeds a herbicidally effective amount of a synergistic herbicidal composition that includes bromoxynil and a protoporphyrinogen oxidase (PPO) inhibitor are disclosed.

This application is a Continuation of U.S. application Ser. No.14/939,556, filed on Nov. 12, 2015, which claims the benefit of U.S.Provision Application No. 62/079,682, filed on Nov. 13, 2014.

FIELD OF THE DISCLOSED SUBJECT MATTER

The presently disclosed subject matter relates to compositionscontaining bromoxynil and protoporphyrinogen oxidase (PPO) inhibitors,and methods for controlling volunteer or herbicide resistant crop weedsusing those compositions.

BACKGROUND

One of the more preferred methods of controlling weeds in crops involvesthe post-emergent control of weeds wherein herbicide(s) are appliedafter the crop in question has emerged from the soil. Post-emergentcontrol is desirable as it requires the application of herbicide onlywhere an infestation of weeds is present. In contrast, pre-emergentcontrol requires the application of herbicide early in the growingseason before most weeds have germinated, with the result that suchchemicals must be employed throughout a field even if they wouldultimately not be needed.

There are approximately 20 million acres of canola grown in westernCanada. At harvest canola crops leave an average of 2-3 bushels per acreof seed in the field, or at least 20 times the normal seeding rate.Canola seed can remain viable in the soil for 2 to 3 years, and withshortened crop rotations, volunteer canola has become a major weed pestin crops, including canola crops.

Bromoxynil (3,5-dibromo-4-hydroxybenzonitrile), is an effectivepost-emergent herbicide for a number of weeds, particularly broadleafweeds, including volunteer canola.

Protoporphyrinogen oxidase (PPO) is an enzyme found in both plants andanimals, which is responsible for the seventh step in the biosynthesisof protoporphyrin IX. This porphyrin is the biosynthetic precursor ofhemoglobin in animals and chlorophyll in plants. The enzyme catalyzesthe dehydrogenation of protoporphyrinogen IX to form protoporphyrin IX.

Protoporphyrinogen oxidase inhibitors are herbicides that act byblocking the production of chlorophyll and heme in a plant, causing anaccumulation of protoporphyrinogen IX that is ultimately toxic to theplant.

A majority of the canola planted in Canada and the USA has beengenetically modified to be tolerant to glyphosate or glufosinate.Therefore these herbicides, when used as a burn down treatment on afield prior to seeding with canola seed, fail to control canola weeds. Asolution to this problem is described herein.

SUMMARY OF THE DISCLOSED SUBJECT MATTER

It has now been discovered that bromoxynil, when used in combinationwith a Protoporphyrinogen oxidase (PPO) inhibitor, is surprisinglyeffective at controlling broadleaf weeds, showing synergism with regardto volunteer crop weed control, including canola which are resistant toglyphosate and glufosinate.

The purpose and advantages of the disclosed subject matter will be setforth in, and apparent from, the description that follows, as well aswill be learned by practice of the disclosed subject matter. Additionaladvantages of the disclosed subject matter will be realized and attainedby the methods and compositions particularly pointed out in the writtendescription and claims hereof.

One aspect of the invention is directed to a method of selectivelycontrolling glyphosate- or glufosinate-resistant weed or glyphosate- orglufosinate-resistant volunteer crop weeds in a crop, comprisingapplying to the volunteer crop weeds a herbicidally effective amount ofa herbicidal composition comprising bromoxynil and a protoporphyrinogenoxidase (PPO) inhibitor. In one embodiment, the PPO inhibitor isselected from the group consisting of carfentrazone,carfentrazone-ethyl, sulfentrazone, fluthiacet-methyl, saflufenacil, andmixtures of two or more thereof; and is preferably selected fromcarfentrazone or carfentrazone-ethyl. More preferably the PPO inhibitorcomprises carfentrazone-ethyl.

In one embodiment of the method, the herbicidal composition is appliedto the field when the volunteer crop weeds are in the 1-6 leaf stage.Volunteer crop weeds can be selected from the group consisting ofcanola, genetically modified canola, soybean and genetically modifiedsoybean. The crop containing these volunteer crop weeds can be selectedfrom the group consisting of genetically modified and non-modified corn,wheat, oat, rye, soybean, cotton, flax, jute, rape, canola, linseed,sesame, safflower, sunflower, clover, beet, sugar beet, sorghum, millet,rice, peanut, pea, bean, cucumber, pepper, melon, cabbage, onion,squash, lettuce, asparagus, eggplant, tomato, tobacco, flower seed andturfgrass. In one embodiment the crop is selected from the groupconsisting of canola, genetically modified canola, and mixtures thereof,and the volunteer crop weed is selected from the group consisting ofcanola, genetically modified canola and mixtures thereof. In oneembodiment the crop is glyphosate- or glufosinate-resistant canola, andthe volunteer crop weed is glyphosate- or glufosinate-resistant canola.

In one embodiment of the method the herbicidal composition is applied toa field as a burn down treatment in order to eliminate the emergedweeds, including volunteer crop weeds, prior to seeding the desired cropwhich crop may include genetically modified or non-modified corn, wheat,oat, rye, soybean, cotton, flax, jute, rape, canola, linseed, sesame,safflower, sunflower, clover, beet, sugar beet, sorghum, millet, rice,peanut, pea, bean, cucumber, pepper, melon, cabbage, onion, squash,lettuce, asparagus, eggplant, tomato, tobacco, flower seed andturfgrass.

In one embodiment of the method the applied composition comprises a tankmix of formulated bromoxynil and a formulated protoporphyrinogen oxidase(PPO) inhibitor. In one embodiment the PPO inhibitor iscarfentrazone-ethyl. In one embodiment the tank mix further comprisesglyphosate or glufosinate.

In one embodiment the applied rate of bromoxynil and/or the applied rateof the protoporphyrinogen oxidase inhibitor is less than the labeled orregistered application rate for control of the crop represented by thevolunteer crop weed. In one embodiment the applied rate of bromoxyniland the applied rate of carfentrazone-ethyl are each half of theirregistered rates for control of the crop represented by the volunteercrop weed.

In one embodiment of the method, the applied composition providessynergistic control of the volunteer crop weed. In one embodiment,control of the volunteer crop weed is effective through at least 21 dayspost treatment.

Another aspect of the invention is directed to a synergistic herbicidalcomposition comprising bromoxynil and a protoporphyrinogen oxidaseinhibitor (PPO) in a ratio between about 4:1 and about 16:1 by weight,wherein application of an effective amount of the synergistic herbicidalcomposition is effective to selectively control volunteer crop weeds ina crop. In one embodiment the synergistic herbicidal composition furthercomprises glyphosate or glufosinate. In one embodiment the PPO inhibitoris selected from the group consisting of carfentrazone,carfentrazone-ethyl, sulfentrazone, fluthiacet-methyl, saflufenacil, andmixtures of two or more thereof. In one embodiment theprotoporphyrinogen oxidase inhibitor comprises carfentrazone-ethyl. Inone embodiment the synergistic herbicidal composition comprisescarfentrazone-ethyl and further comprises glyphosate.

DETAILED DESCRIPTION

The present document discloses compositions and methods that providesynergistic efficacy for controlling crop weeds in crops. This includesone of the most problematic weeds in Canadian agriculture, volunteercanola. The compositions and methods disclosed herein are advantageousin that this synergistic combination now provides a new tool to controlcrop weeds which are resistant to glyphosate and glufosinate due togenetic modification.

One aspect of the invention is directed to a method of selectivelycontrolling glyphosate- or glufosinate-resistant volunteer crop weeds ina crop, comprising applying to the volunteer crop weeds a herbicidallyeffective amount of a herbicidal composition comprising bromoxynil and aprotoporphyrinogen oxidase (PPO) inhibitor. In one embodiment, the PPOinhibitor is selected from the group consisting of carfentrazone,carfentrazone-ethyl, sulfentrazone, fluthiacet-methyl, saflufenacil, andmixtures of two or more thereof. In a preferred embodiment the PPOinhibitor comprises carfentrazone or carfentrazone-ethyl. In a morepreferred embodiment the PPO inhibitor comprises carfentrazone-ethyl.

In another embodiment, the protoporphyrinogen oxidase (PPO) inhibitor isselected from diphenyl ethers, oxadiazoles, cyclic imides or pyrazoles.Examples of these PPO classes include, without limitation, acifluorfen,acifluorfen-sodium, azafenidin, bifenox, butafenacil, chlomethoxyfen,chlornitrofen, ethoxyfen-ethyl, fluorodifen, fluoroglycofen-ethyl,fluoronitrofen, fomesafen, furyloxyfen, halosafen, lactofen, nitrofen,nitrofluorfen, oxyfluorfen, flumiclorac-pentyl, flumioxazine,profluazol, pyrazogyl, oxadiargyl, oxadiazon, pentoxazone, fluazolate,pyraflufen-ethyl, benzfendizone, butafenacil, cinidon-ethyl,flumipropyn, flupropacil, fluthiacet-methyl, thidiazimin, azafenidin,carfentrazone, carfentrazone-ethyl, sulfentrazone, saflufenacil,flufenpyr-ethyl, ET-751, JV 485, nipyraclofen, or mixtures of two ormore thereof. Preferably the PPO inhibitors are selected from the groupconsisting of carfentrazone, sulfentrazone, fluthiacet-methyl,saflufenacil, and mixtures of two or more thereof. More preferably thePPO inhibitor comprises carfentrazone, still more preferablycarfentrazone-ethyl.

The herbicidal compositions of the present disclosure can be in anyconventional agriculturally useful form, for example, in the form of atwin pack, or in a ready-to-use formulation, or in the form of a tankmix. Additionally, the active compounds can be supplied (eitherseparately or pre-mixed) in any appropriate formulation type, forexample an emulsion concentrate (EC), a suspension concentrate (SC), asuspo-emulsion (SE), a capsule suspension (CS), a water dispersiblegranule (WG), an emulsifiable granule (EG), a water in oil emulsion(EO), an oil in water emulsion (EW), a micro-emulsion (ME), an oildispersion (OD), an oil miscible flowable (OF), an oil miscible liquid(OL), a soluble concentrate (SL), an ultra-low volume suspension (SU),an ultra-low volume liquid (UL), a dispersible concentrate (DC), awettable powder (WP), a mixed heterogeneous formulation of CS and EW(ZW), or any other technically feasible formulation in combination withagriculturally acceptable adjuvants. For tank mixing, commercialformulations of bromoxynil and a PPO inhibitor are combined in a tankprior to application, in the appropriate ratio to provide the targetedweight ratio of the active ingredients. In one embodiment, theherbicidal compositions of the present disclosure are tank mixes. Inanother embodiment, the herbicidal compositions of the presentdisclosure are supplied as premix emulsifiable concentrates (ECs).

Rates of application of the composition, or tank-mixed separatelyformulated active ingredients, will vary according to prevailingconditions such as targeted volunteer crop weeds, degree of infestation,weather conditions, soil conditions, crop species, mode of application,and application time. Compositions containing bromoxynil and a PPOinhibitor can be applied as sprays, such as water-dispersibleconcentrates, wettable powders, or water-dispersible granules. In oneembodiment, the rate of application for active ingredient (“ai”) (e.g.bromoxynil and a PPO inhibitor) is from about 30 g ai/acre to about 120gai/acre, preferably about 30 g ai/acre to about 65 g ai/acre.

In one embodiment, the present disclosure describes an agriculturalformulation or tank mix containing at least two agriculturally activeingredients: bromoxynil and a PPO inhibitor. In one embodiment, the PPOinhibitor is selected from carfentrazone, carfentrazone-ethyl,sulfentrazone, fluthiacet-methyl, saflufenacil, or mixtures of two ormore thereof. In another embodiment, the PPO inhibitor is preferablycarfentrazone-ethyl. According to one aspect of this embodiment, thebromoxynil and the PPO inhibitor are present in a ratio between about4:1 and about 31:1 by weight. In one embodiment, the bromoxynil and thePPO inhibitor are present in a ratio between about 4:1 and about 16:1 byweight. In a preferred embodiment, the bromoxynil and the PPO inhibitorare present in a ratio between about 5:1 and about 16:1. In a morepreferred embodiment, the bromoxynil and the PPO inhibitor are presentin a ratio between about 8:1 and about 16:1. In one embodiment thebromoxynil and the PPO inhibitor are present in a ratio of about 5:1. Inone embodiment the bromoxynil and the PPO inhibitor are present in aratio of about 8:1. In one embodiment the bromoxynil and the PPOinhibitor are present in a ratio of about 10:1. In one embodiment thebromoxynil and the PPO inhibitor are present in a ratio of about 16:1.These can be commercial formulations that are tank mixed at the time ofapplication, or a suitable premix formulation. Suitable premixformulations include, without limitation, suspension concentrate (SC)and emulsifiable concentrate (EC). In a further aspect, the agriculturalformulation or tank mix contains an additional herbicide. The additionalherbicide can be selected, without limitation, from atrazine,glyphosate, glufosinate, pyroxasulfone, dicamba, diflufenzopyr,nicosulfuron, salts thereof, or mixtures of two or more thereof. In oneaspect the additional herbicide is glyphosate.

The average size or maturity of the volunteer crop weed is indicated bythe leaf stage of the plant (total number of leaves on the plant), andin one embodiment, is 1 to about 6 leaves, or more. In one embodimentthe average crop weed is in an early leaf stage having about 2 to about4 leaves. In other embodiments, the average crop weed is in anintermediate leaf stage having 4 to about 6 leaves, or greater than 4leaves, or about 5 to about 6 leaves or more. In another embodiment, theaverage crop weed is in a late stage having greater than 6 leaves. Forthe purposes of the present disclosure, these latter stages, with 4leaves or more, are considered more mature weeds.

In one embodiment the applied composition is effective to control moremature volunteer crop weeds, with more mature weeds being indicated bythe 4-6 leaf stage, or larger. In one embodiment volunteer crop weeds atabout the 2-6 leaf stage are effectively controlled. In one embodimentvolunteer crop weeds at about the 2-4 leaf stage are effectivelycontrolled. In another embodiment volunteer crop weeds at about the moremature 4-6 leaf stage are effectively controlled. In yet anotherembodiment volunteer crop weeds at about the more mature 4-6 leaf orgreater stage are effectively controlled. In one embodiment thevolunteer crop weeds comprise canola or genetically modified canola, orglyphosate- or glufosinate-resistant canola.

The volunteer crop weeds can be selected from the group consisting ofcanola, genetically modified canola, soybean and genetically modifiedsoybean. Other susceptible weed species include, without limitation,waterhemp, lambsquarters, velvetleaf, palmer amaranth, pigweed, morningglory, cocklebur, ragweed, broadleaf signalgrass, foxtail, crabgrass,volunteer soybean, nutsedge, Egyptian crowfoot grass, fumitory,denticulate medick, lesser swine cress, brown beetle grass, junglegrass, tendla, false amaranth, common purslane and field bindweed. Inone embodiment the crop is selected from the group consisting ofgenetically modified and non-modified corn, wheat, oat, rye, soybean,cotton, flax, jute, rape, canola, linseed, sesame, safflower, sunflower,clover, beet, sugar beet, sorghum, millet, rice, peanut, pea, bean,cucumber, pepper, melon, cabbage, onion, squash, lettuce, asparagus,eggplant, tomato, tobacco, flower seed and turfgrass. In anotherembodiment, the crop to be treated is wheat, oat, rye, soybean, cotton,flax, jute, or rape.

In another embodiment, the crop weed is selected from the groupconsisting of canola, genetically modified canola, and mixtures thereof.In a specific embodiment the crop weed is selected from the groupconsisting of canola, genetically modified canola, and mixtures thereof,and the volunteer crop weed is genetically modified canola. In oneembodiment the crop weed is glyphosate- or glufosinate-resistant canola.

In one embodiment of the method the herbicidal composition is applied toa field as a burn down treatment in order to eliminate the emergedweeds, including volunteer crop weeds, prior to seeding the desiredcrop, for example, canola or flax. The seeded canola crop can begenetically modified or a non-modified variety. The volunteer crop weedscan comprise canola, either genetically modified, a non-modified varietyor combinations thereof.

The compositions and tank mixes of the present disclosure canadditionally comprise further crop protection agents, selected from thegroup consisting of fungicides, insecticides, nematocides, plant growthregulators, herbicides other than bromoxynil and PPO herbicides, andfertilizers. In one embodiment the composition comprises a tank mix offormulated bromoxynil and a formulated protoporphyrinogen oxidase (PPO)inhibitor. In one embodiment the PPO inhibitor is carfentrazone-ethyl.In one embodiment the tank mix further comprises glyphosate orglufosinate. In a preferred embodiment the tank mix further comprisesglyphosate.

In one embodiment the applied rate of bromoxynil and/or the applied rateof the protoporphyrinogen oxidase inhibitor is less than the registeredapplication rate for control of the crop represented by the volunteercrop weed. In one embodiment the applied rate of bromoxynil and theapplied rate of carfentrazone-ethyl are each half of their registeredrates for control of the crop represented by the volunteer crop weed.Carfentrazone-ethyl is labeled or registered at a use rate of 18 gai/hato control volunteer canola with no residual carry over that couldpotentially damage the establishing canola crop. Bromoxynil isregistered at a use rate of 280 gai/ha to control volunteer canola, alsowith no residual carry over that could potentially damage anestablishing canola crop seeded post-treatment.

In at least one aspect of the present invention, the inventors conductedField Trials in Georgia, US, in 2013, and in 2014 in Canada and havesuccessfully shown that a tank mix of carfentrazone at 9 gai/ha andbromoxynil at 140 gai/ha gives control of glyphosate- orglufosinate-resistant canola significantly greater than either productalone at its registered use rate. Thus, in one embodiment it has beendemonstrated that one-half of the registered use rates of bothcarfentrazone-ethyl and bromoxynil when tank mixed provide good controlof volunteer canola greater than either product alone at the fullregistered use rate. See Examples.

In one embodiment, the control of the volunteer crop weed is effectivethrough at least 21 days post-treatment, preferably at least 35 dayspost treatment. In one embodiment of the method, the applied compositionprovides synergistic control of the volunteer crop weed.

Thus, another aspect of the invention is directed to a synergisticherbicidal composition comprising bromoxynil and a protoporphyrinogenoxidase inhibitor (PPO) in a ratio between about 4:1 and about 16:1,preferably about 8:1 to about 16:1, wherein application of an effectiveamount of the synergistic herbicidal composition selectively controlsvolunteer crop weeds in a crop. In one embodiment the synergisticherbicidal composition further comprises glyphosate or glufosinate. Inone embodiment the PPO inhibitor is selected from the group consistingof carfentrazone, carfentrazone-ethyl, sulfentrazone, fluthiacet-methyl,saflufenacil, and mixtures of two or more thereof. In one embodiment theprotoporphyrinogen oxidase inhibitor comprises carfentrazone-ethyl. Inone embodiment the synergistic herbicidal composition comprisescarfentrazone-ethyl and further comprises glyphosate.

In another aspect of the invention, mixtures containingcarfentrazone-ethyl, glyphosate and bromoxynil octanoic acid esterexhibit a synergistic effect in control of volunteer canola whencompared to the control of canola using mixtures ofcarfentrazone-ethyl/glyphosate and bromoxynil octanoic acidester/glyphosate. In one embodiment, the synergy is maintained for atleast 5, 7, 10, 14, 19, 21, 35, or 45 days after planting. In anotherembodiment, the synergistic effect is provided for mature stage canolaweeds for at least 5, 7, 10, 14, 19, 21, 35, or 45 days after planting.In a more preferred embodiment, the synergistic effect is provided forvolunteer, genetically modified or glyphosate resistant canola having atleast 6 leaves.

The compositions of the present disclosure can also include apreservative. Suitable preservatives include, but are not limited to,C₁₂ to C₁₅ alkyl benzoates, alkyl p-hydroxybenzoates, aloe vera extract,ascorbic acid, benzalkonium chloride, benzoic acid, benzoic acid estersof C₉ to C₁₅ alcohols, butylated hydroxytoluene, butylatedhydroxyanisole, tert-butylhydroquinone, castor oil, cetyl alcohols,chlorocresol, citric acid, cocoa butter, coconut oil, diazolidinyl urea,diisopropyl adipate, dimethyl polysiloxane, DMDM hydantoin, ethanol,ethylenediaminetetraacetic acid, fatty acids, fatty alcohols, hexadecylalcohol, hydroxybenzoate esters, iodopropynyl butylcarbamate, isononyliso-nonanoate, jojoba oil, lanolin oil, mineral oil, oleic acid, oliveoil, parabens, polyethers, polyoxypropylene butyl ether,polyoxypropylene cetyl ether, potassium sorbate, propyl gallate,silicone oils, sodium propionate, sodium benzoate, sodium bisulfite,sorbic acid, stearic fatty acid, sulfur dioxide, vitamin E, vitamin Eacetate and derivatives, esters, salts and mixtures thereof. Preferredpreservatives include sodium o-phenylphenate,5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one,and 1,2-benisothiazolin-3-one.

DEFINITIONS

As used in this application and unless otherwise indicated the term“herbicide” refers to a compositional mixture that is produced, sold, orused in a field in order to kill or otherwise inhibit unwanted plantssuch as, but not limited to, deleterious or annoying weeds, broadleafplants, grasses, and sedges; and can be used for crop protection,edifice protection or turf protection. The term “herbicide” includes theend-use herbicidal product. This composition can be a pure compound, asolution of chemical compounds, a mixture of chemical compounds, anemulsion, a suspension, a solid-liquid mixture, or a liquid-liquidmixture. The term “herbicide” also refers to the product that passesthrough the commercial channels from the manufacturer to the ultimateend user who can either apply the herbicide to the affected field assold, or mix it with other excipients.

The term “weed” means and includes any plant which grows where it is notwanted, including volunteer crop plants or insecticide resistant plants.

The term “effective” or “herbicidally effective amount” means an amountnecessary to produce an observable herbicidal effect on unwanted plantgrowth, including one or more of the effects of necrosis, death, growthinhibition, reproduction inhibition, inhibition of proliferation, andremoval, destruction, or otherwise diminishing the occurrence andactivity of unwanted plants.

The term “herbicidally active ingredient” means the active ingredient inthe herbicide that causes the herbicide to prevent, destroy, repel ormitigate any weed. Other ingredients of the herbicide that are notherbicidally active ingredients are excipients that aid in forming,storing, or delivering herbicidally active ingredient to the target.Examples of excipients in the present embodiment include, withoutlimitation, an organic liquid in which herbicidally active ingredient isdissolved, a polyurea shell, a water-soluble polymer, and one or moresalts.

The definition of the term “herbicidal composition” refers to aherbicide, and in addition, to any composition that comprises aherbicidally active ingredient. This composition can be a solution or amixture. Further, the definition of the term “herbicidal composition”also refers to a product intended for use in manufacruting, or anyproduct intended for formulation or repackaging into other agriculturalproducts.

As used herein, the terms “synergy” and “synergistic”, or the phrase “ina synergistic manner”, refer to the in vivo interaction of two or morebiologically active compounds, in the present case bromoxynil and a PPOinhibitor, so that their combined effect when administered together isgreater than the sum of the effects observed when each is administeredindividually. That is, the herbicidal effect of administering thecombination of bromoxynil and a PPO inhibitor as disclosed above, isgreater than the sum of the herbicidal effects of administeringbromoxynil alone and the PPO inhibitor alone at their use rates. In thisway the applied rate of the herbicidal combination can be lower than theregistered use rates, thereby reducing the total chemical burden on thefield to which such a combination is applied. In the present disclosure,the method of Colby is used to establish synergism (see Colby, S. R.,“Calculating Synergistic and Antagonistic Responses of HerbicideCombinations”, Weeds 1967, 15, pg 20-22, which is incorporated herein byreference). Thus, the presence of a synergistic effect between the twoactive ingredients is established with the aid of the Colby equation:E=X+Y−(XY/100). See the Examples presented below. In these examples thevolunteer canola weed is genetically modified to be tolerant toglyphosate (ROUNDUP READY® canola, Monsanto), therefore the glyphosatepresent in the applied typical burn down formulations should have noeffect on this volunteer crop weed species. Further, calculation ofsynergy using the Colby equation zeroes out any effect of glyphosate,since it is present at the same rate in all applications.

As used herein, the terms “labeled use rate” or “registered use rate” or“labeled application rate” or “registered application rate” as appliedto herbicidal compositions refer to the rate of application to a fieldcontaining crops and/or weeds, which rate has been established by theagrochemical industry, as reflected in Environmental Protection Agency(EPA) regulations, to be appropriate for control of the indicated weedspecies. The registered use rate is reflected on the commercialformulation packaging in an appropriate label. Thus, one-half theregistered use rate would indicate application of only half of thelabeled rate of a herbicidal formulation, with respect to the gaiapplied.

The following examples serve only to illustrate the invention and shouldnot be interpreted as limiting the scope of the invention in any way,since further modifications encompassed by the disclosed invention willbe apparent to those skilled in the art. All such modifications aredeemed to be within the scope of the invention as disclosed in thepresent specification and claims.

EXAMPLES Example 1 Control of Glyphosate-Resistant Canola with Mixturesof Glyphosate, Carfentrazone-Ethyl and Bromoxynil

Test plots located in Winnipeg, Manitoba, Canada (4 replicates for eachrate, 13 m² each) were seeded with ROUNDUP READY® canola (RR® canola).Once the canola emerged and was at the 2 to 4-leaf stage, the plots weresprayed with the test at a spray volume of 100 L/ha. The test plots wereevaluated for % control of canola as compared to untreated controlplots. In order to provide a measure of the effectiveness of aherbicide's performance weed control ratings were based on visualobservations of the presence or absence of canola. Ratings were based ona 0 to 100 rating system, where 0 equals no control and 100 equalscomplete control, which generally makes use of direct-percentagefigures. In this system the standard basis for comparison is anuntreated check. Counts are made of canola found in the untreated areaof the study. This provides a basis to give a precise representation ofboth canola in the untreated plots and degree of control provided byvarious chemical treatments.

The presence of a synergistic effect between the two active ingredientsis established with the aid of the Colby equation (see Colby, S. R.,“Calculating Synergistic and Antagonistic Responses of HerbicideCombinations”, Weeds 1967, 15, pg 20-22): E=X+Y−(XY/100). In the presentexample, X is represented by a certain mixture of glyphosate (ROUNDUPWEATHERMAX® Herbicide from Monsanto) and carfentrazone-ethyl (AIM® ECHerbicide from FMC Corporation) and Y is a mixture of glyphosate(ROUNDUP WEATHERMAX® Herbicide from Monsanto) and bromoxynil octanoicacid ester (PARDNER® Herbicide from Bayer CropScience).

Using the method of Colby, the presence of a synergistic interactionbetween two active ingredients is established by first calculating theexpected activity, ‘E’, of the mixture based on activities of the twocomponents applied alone. In the equation above, ‘X’ is the herbicidalactivity in percentage control of glyphosate and carfentrazone-ethylapplied as a mixture at rate ‘x’. The ‘Y’ term is the herbicidalactivity of glyphosate and bromoxynil applied as a mixture at rate ‘y’.The equation calculates ‘E’, the herbicidal activity of the mixture of‘X’ at rate ‘x’ with ‘Y’ at rate ‘y’. If ‘E’ is lower than the observedactivity, synergy is present. If the herbicidal effect is strictlyadditive and no interaction has occurred, ‘E’ will be equal to or higherthan the observed activity. Tables 1A and 1B below summarize (average of4 replicates) the % control of canola and the expected verses observed %control of mixtures of carfentrazone-ethyl, glyphosate and bromoxyniloctanoic acid ester in two trials.

TABLE 1A % Control of RR ® Canola Trial 1, Manitoba, Canada % Control ofCanola, 2-4 leaf stage Treatment Rate 8 DAT 18 DAT 35 DAT AIM ® (9gai/ha) + 65.5 63.5 48.5 ROUNDUP WEATHERMAX ® (450 gai/ha) AIM ® (18gai/ha) + 78.5 76.5 65.0 ROUNDUP WEATHERMAX ® (450 gai/ha) PARDNER ®(140 gai/ha) + 76.3 75.8 58.3 ROUNDUP WEATERMAX ® (450 gai/ha) AIM ® (9gai/ha) + Expected = 91.8 Expected = 91.1 Expected = 78.5 ROUNDUPObserved = 91.8 Observed = 95.0 Observed = 89.5 WEATHERMAX ® (450gai/ha) + PARDNER ® (140 gai/ha) AIM ® (18 gai/ha) + Expected = 94.9Expected = 94.3 Expected = 85.4 ROUNDUP Observed = 97.0 Observed = 97.8Observed = 97.3 WEATHERMAX ® (450 gai/ha) + PARDNER ® (140 gai/ha)

TABLE 1B % Control of RR ® Canola Trial 2, Manitoba, Canada % Control ofCanola, 2-4 leaf stage Treatment Rate 4 DAT 12 DAT 19 DAT AIM ® (9gai/ha) + 45.0 56.0 58.8 ROUNDUP WEATHERMAX ® (450 gai/ha) AIM ® (18gai/ha) + 40.5 62.5 68.5 ROUNDUP WEATHERMAX ® (450 gai/ha) PARDNER ®(140 gai/ha) + 47.8 58.3 66.3 ROUNDUP WEATERMAX ® (450 gai/ha) AIM ® (9gai/ha) + Expected = 71.3 Expected = 81.7 Expected = 86.1 ROUNDUPObserved = 78.5 Observed = 91.8 Observed = 93.3 WEATHERMAX ® (450gai/ha) + PARDNER ® (140 gai/ha) AIM ® (18 gai/ha) + Expected = 68.9Expected = 84.4 Expected = 89.4 ROUNDUP Observed = 76.8 Observed = 93.8Observed = 94.3 WEATHERMAX ® (450 gai/ha) + PARDNER ® (140 gai/ha)

As can be seen from the Tables above, mixtures containingcarfentrazone-ethyl, glyphosate and bromoxynil exhibit a synergisticeffect in control of canola when compared to mixtures ofcarfentrazone-ethyl/glyphosate and bromoxynil octanoic acidester/glyphosate.

Example 2 Control of Glyphosate-Resistant Canola with Mixtures ofGlyphosate, Carfentrazone-Ethyl and Bromoxynil

Test plots located in Sparks Georgia, USA (4 replicates for each rate,13 m² each) were seeded with ROUNDUP READY® canola (RR® canola). Oncethe canola emerged and was at the 1 to 3-leaf or 4 to 6 leaf stage, theplots were sprayed with the test at a spray volume of 100 L/ha. The testplots were evaluated for % control of canola as compared to untreatedcontrol plots. In order to provide a measure of the effectiveness of aherbicide's performance weed control ratings were based on visualobservations of the presence or absence of canola. Ratings were based ona 0 to 100 rating system, where 0 equals no control and 100 equalscomplete control, which generally makes use of direct-percentagefigures.

In this system the standard basis for comparison is an untreated check.Counts are made of canola found in the untreated area of the study. Thisprovides a basis to give a precise representation of both canola in theuntreated plots and degree of control provided by various chemicaltreatments. The trials were read at 7, 14 and 21 days after treatment(DAT). The presence of a synergistic effect between the two activeingredients is established with the aid of the Colby equation (seeColby, S. R., “Calculating Synergistic and Antagonistic Responses ofHerbicide Combinations”, Weeds 1967, 15, pg 20-22): E=X+Y−(XY/100). Inthe present example, X is represented by a certain mixture of glyphosate(ROUNDUP WEATHERMAX® Herbicide from Monsanto) and carfentrazone-ethylAIM® EC Herbicide from FMC Corporation) and Y is a mixture of glyphosate(ROUNDUP WEATHERMAX® Herbicide from Monsanto) and bromoxynil octanoicacid ester (MAESTRO® 2EC Herbicide from Nufarm).

Table 2 below summarizes (average of 4 replicates) the % control ofcanola and the expected verses observed % control of mixtures ofcarfentrazone-ethyl, glyphosate and bromoxynil octanoic acid ester intwo trials.

TABLE 2 % Control of RR ® Canola, Georgia, USA % Control of Canola 7 DAT7 DAT 14 DAT 14 DAT 21 DAT 21 DAT Treatment Rate 1-3 leaf 4-6 leaf 1-3leaf 4-6 leaf 1-3 leaf 4-6 leaf AIM ® (9 gai/ha) + 5 0 22 0 36 1 ROUNDUPWEATHERMAX ® (450 gai/ha) AIM ® (18 gai/ha) + 16 0 49 1 79 5 ROUNDUPWEATHERMAX ® (450 gai/ha) AIM ® (27 gai/ha) + 20 1 54 7 81 12 ROUNDUPWEATHERMAX ® (450 gai/ha) MAESTRO ® 27 0 78 5 78 10 (140 gai/ha) +ROUNDUP WEATERMAX ® (450 gai/ha) MAESTRO ® 46 0 96 15 76 42 (280gai/ha) + ROUNDUP WEATERMAX ® (450 gai/ha) AIM ® (9 gai/ha) + ExpectedExpected Expected Expected Expected Expected ROUNDUP 31 0 83 5 86 11WEATHERMAX ® Observed Observed Observed Observed Observed Observed (450gai/ha) + 59 1 94 12 95 41 MAESTRO ® (140 gai/ha) AIM ® (9 gai/ha) +Expected Expected Expected Expected Expected Expected ROUNDUP 49 0 97 1585 43 WEATHERMAX ® Observed Observed Observed Observed Observed Observed(450 gai/ha) + 85 11 98 42 87 53 MAESTRO ® (280 gai/ha) AIM ® (18gai/ha) + Expected Expected Expected Expected Expected Expected ROUNDUP39 0 89 6 95 15 WEATHERMAX ® Observed Observed Observed ObservedObserved Observed (450 gai/ha) + 80 19 97 33 99 68 MAESTRO ® (140gai/ha) AIM ® (18 gai/ha) + Expected Expected Expected Expected ExpectedExpected ROUNDUP 55 0 98 16 95 45 WEATHERMAX ® Observed ObservedObserved Observed Observed Observed (450 gai/ha) + 85 21 99 53 99 76MAESTRO ® (280 gai/ha) AIM ® (27 gai/ha) + Expected Expected ExpectedExpected Expected Expected ROUNDUP 42 1 90 12 96 21 WEATHERMAX ®Observed Observed Observed Observed Observed Observed (450 gai/ha) + 7220 99 50 91 71 MAESTRO ® (140 gai/ha) AIM ® (27 gai/ha) + ExpectedExpected Expected Expected Expected Expected ROUNDUP 57 1 98 21 95 49WEATHERMAX ® Observed Observed Observed Observed Observed Observed (450gai/ha) + 91 39 100 75 100 83 MAESTRO ® (280 gai/ha)

As can be seen from Table 2, above, mixtures containingcarfentrazone-ethyl, glyphosate and bromoxynil octaonic acid esterexhibit a synergistic effect in control of canola when compared to thecontrol of canola using mixtures of carfentrazone-ethyl/glyphosate andbromoxynil octanoic acid ester/glyphosate. In fact, in some tests thethree-way mixture of the present invention exhibits up to 3 times morecontrol when compared to individual mixtures ofcarfentrazone-ethyl/glyphosate and bromoxynil octanoic acidester/glyphosate.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the following claims.

What is claimed is:
 1. A method of selectively controlling glyphosate- or glufosinate-resistant volunteer crop weeds in a crop, comprising applying to said volunteer crop weeds a herbicidally effective amount of a composition comprising bromoxynil and a protoporphyrinogen oxidase inhibitor.
 2. The method of claim 1, wherein said protoporphyrinogen oxidase inhibitor is selected from the group consisting of carfentrazone, sulfentrazone, fluthiacet-methyl, saflufenacil, and mixtures of two or more thereof.
 3. The method of claim 1, wherein said protoporphyrinogen oxidase inhibitor comprises carfentrazone.
 4. The method of claim 1, wherein said volunteer crop weeds are in the 1-6 leaf stage.
 5. The method of claim 4, wherein said volunteer crop weeds are selected from the group consisting of canola, genetically modified canola, soybean and genetically modified soybean.
 6. The method of claim 1, wherein said crop is selected from the group consisting of genetically modified and non-modified corn, wheat, oat, rye, soybean, cotton, flax, jute, rape, canola, linseed, sesame, safflower, sunflower, clover, beet, sugar beet, sorghum, millet, rice, peanut, pea, bean, cucumber, pepper, melon, cabbage, onion, squash, lettuce, asparagus, eggplant, tomato, tobacco, flower seed and turfgrass.
 7. The method of claim 1, wherein said crop is selected from the group consisting of canola, genetically modified canola, and mixtures thereof, and said volunteer crop weed is selected from the group consisting of canola, genetically modified canola and mixtures thereof.
 8. The method of claim 1, wherein said composition comprises a tank mix of formulated bromoxynil and a formulated protoporphyrinogen oxidase inhibitor.
 9. The method of claim 8, wherein said protoporphyrinogen oxidase inhibitor is carfentrazone-ethyl.
 10. The method of claim 1, wherein said composition further comprises glyphosate or glufosinate.
 11. The method of claim 1, wherein the applied rate of bromoxynil and/or the applied rate of protoporphyrinogen oxidase inhibitor is less than the registered application rate for control of the crop represented by the volunteer crop weed.
 12. The method of claim 9, wherein the applied rate of bromoxynil and the applied rate of carfentrazone-ethyl are each half of their registered rates for control of the crop represented by the volunteer crop weed.
 13. The method of claim 1, wherein said composition provides synergistic control of said volunteer crop weed.
 14. The method of claim 1, wherein control of said volunteer crop weed is effective through at least 21 days post treatment.
 15. The method of claim 4, which is effective to control more mature volunteer crop weeds.
 16. A synergistic herbicidal composition comprising bromoxynil and a protoporphyrinogen oxidase inhibitor in a ratio between about 4:1 and about 16:1 by weight, wherein said synergistic herbicidal composition is effective to selectively control volunteer crop weeds in a crop.
 17. The synergistic herbicidal composition of claim 16, further comprising glyphosate or glufosinate.
 18. The synergistic herbicidal composition of claim 16, wherein said protoporphyrinogen oxidase inhibitor is selected from the group consisting of carfentrazone, sulfentrazone, fluthiacet-methyl, saflufenacil, and mixtures of two or more thereof.
 19. The synergistic herbicidal composition of claim 16, wherein said protoporphyrinogen oxidase inhibitor comprises carfentrazone.
 20. The synergistic herbicidal composition of claim 19, further comprising glyphosate. 